Added readme.

README.md

@@ -0,0 +1,3 @@
+# Advent of Rust 2024
+
+A few of the solutions for [Advent of Code 2024](https://adventofcode.com/2024) in Rust.

src/main.rs

@@ -3,23 +3,14 @@ use std::fs::read_to_string;
 
 fn main() {
     let input = read_to_string("input/day01.txt").unwrap();
-    let part1 = part1(&input);
-    println!("part1: {}", part1);
+    println!("part1: {}", part1(&input));
+    println!("part1: {}", part2(&input));
 }
 
 type Int = i32;
 
 fn part1(input: &str) -> Int {
-    let (mut l, mut r) = input
-        .trim()
-        .lines()
-        .map(|line| line.split_ascii_whitespace().collect_tuple().unwrap())
-        .map(|(x, y)| (x.parse::<Int>().unwrap(), y.parse::<Int>().unwrap()))
-        .fold((vec![], vec![]), |(mut v1, mut v2), (a, b)| {
-            v1.push(a);
-            v2.push(b);
-            (v1, v2)
-        });
+    let (mut l, mut r) = make_lists(input);
 
     l.sort();
     r.sort();
@@ -30,8 +21,32 @@ fn part1(input: &str) -> Int {
         .sum()
 }
 
+fn part2(input: &str) -> Int {
+    let (l, r) = make_lists(input);
+
+    l.iter()
+        .map(|l| r.iter().filter(|r| *r == l).count() as Int * l)
+        .sum()
+}
+
+fn make_lists(input: &str) -> (Vec<Int>, Vec<Int>) {
+    input
+        .trim()
+        .lines()
+        .map(|line| line.split_ascii_whitespace().collect_tuple().unwrap())
+        .map(|(x, y)| (x.parse::<Int>().unwrap(), y.parse::<Int>().unwrap()))
+        .fold((vec![], vec![]), |(mut v1, mut v2), (a, b)| {
+            v1.push(a);
+            v2.push(b);
+            (v1, v2)
+        })
+}
+
 #[cfg(test)]
-const TEST_INPUT: &str = r"
+mod test {
+    use crate::{part1, part2};
+
+    const TEST_INPUT: &str = r"
 3   4
 4   3
 2   5
@@ -40,7 +55,12 @@ const TEST_INPUT: &str = r"
 3   3
 ";
 
-#[test]
-fn test() {
-    assert_eq!(part1(TEST_INPUT), 11);
+    #[test]
+    fn test1() {
+        assert_eq!(part1(TEST_INPUT), 11);
+    }
+    #[test]
+    fn test2() {
+        assert_eq!(part2(TEST_INPUT), 31);
+    }
 }